Which statement describes why mass-based fueling is preferred?

• A. It is less sensitive to air density changes than volumetric fueling
• B. It is unaffected by injector calibration
• C. It requires more injector calibration
• D. It relies on engine speed only

Answer: (A)

Mass-based fueling keeps the air–fuel ratio accurate across changes in air density by metering fuel from the actual mass of air entering the engine. Air density varies with temperature and pressure, so the same air volume can contain more or less mass. If fuel delivery were tied to air volume, those density changes would make the mixture lean or rich. By measuring or calculating the incoming air mass (often with a mass airflow sensor) and adjusting fuel to match that mass, the system maintains the target AFR under different conditions. Injector calibration still matters, but the main benefit is that changing air density no longer disrupts the mixture. The other statements aren’t correct because fueling isn’t driven by engine speed alone, and injector calibration isn’t inherently worse or better merely because fueling is mass-based.